Washing machine appliances generally include a tub for containing wash fluid, e.g., water and detergent, bleach and/or other wash additives. A basket is rotatably mounted within the tub and defines a wash chamber for receipt of articles for washing. During operation of such washing machine appliances, wash fluid is directed into the tub and onto articles within the wash chamber of the basket. The basket or an agitation element can rotate at various speeds to agitate articles within the wash chamber in the wash fluid, to wring wash fluid from articles within the wash chamber, etc.
One issue with presently known washing machine appliances is the balance of the basket within the tub during operation. This issue is of particular concern for vertical axis washing machine appliances. For example, articles loaded within a basket may not be equally weighted about the central axis of the basket. Accordingly, when the basket rotates, in particular during a spin cycle, the imbalance in clothing weight may cause the basket to be out-of-balance within the tub, such that the central axis of the basket is not parallel with the central axis of the tub and/or basket translates within the tub. Such out-of-balance issues can cause the basket to contact the tub during rotation.
Various methods are known for monitoring load balance of washing machine appliances. However, these methods are complicated, expensive to implement, and/or frequently not accurate. Some methods, for example, monitor increases in speed ripple amplitude or peak accelerations. However, these methods may, for example and depending on the type of device, construction of the appliance, and/or speed of operation, not be sufficiently sensitive to out-of-balance indicators, thus causing inaccurate results.
Accordingly, improved methods and apparatus for monitoring load balance in washing machine appliances are desired. In particular, methods and apparatus which provide simple, cost-effective and accurate monitoring would be advantageous.